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A novel strategy for the formation, without the need for organic solvents, of stable giant proteopolymersomes from the highly water-soluble triblock copolymer poly(2,3-dihydroxypropyl methacrylate)...

The Langmuir film formation of poly(ethylene glycol) (PEG)- and poly(methacrylo polyhedral oligomeric silsesquioxane) P(MA-POSS)-based diblock copolymers (PEG5k-b-P(MA-POSS)x) at the air/water interface is investigated. While the Langmuir film formed by the PEG5k collapses at π ≈ 8 mN m−1, the PEG5k-b-P(MA-POSS)x forms a stable film on the water surface revealing various phase transitions in surface pressure vs mean molecular area (π-mmA) isotherm—manifested by various pseudo-plateaus during compression. At higher surface coverage, the π-mmA isotherm exhibits a phase transition that is attributed to the transformation of the P(MA-POSS) monolayer into a multilayer film that is confirmed by AFM measurements of the Langmuir-Blodgett films fabricated before and after the phase transition and direct infrared reflection absorption spectroscopy of the Langmuir film during compression. At a still higher surface pressure, another pseudo-plateau is observed that is assigned to the ultimate film collapse as verified by the Brewster angle microscopy.

We present first results on triazolium-based ionic liquids (ILs) as a novel class of nonderivatizing solvents for cellulose. Despite their chemical similarity to imidazolium cations, the 1,2,3-triazolium cation lacks the isolated ring proton, leading to reduced formation of N-heterocyclic carbenes (NHCs) and therefore to lower reactivity and less unwanted side reactions. We synthesized six ILs based on 1,2,3-triazolium and 1,2,4-triazolium cations. The acetates are room-temperature ionic liquids and dissolve a similar amount of cellulose as the corresponding imidazolium salt. From NMR spectroscopy of the solution, we rule out polymer degradation. The cellulose solubility rises with increasing anion basicity, while being almost independent of the cation. We perform molecular dynamics simulations and compute enthalpies of solvation, which quantitatively fit the experimental solubilities. Trajectory analysis reveals strong hydrogen bonds between acetate anions and cellulose hydroxyl groups, while the cations do not form strong hydrogen bonds with cellulose. Thus, the simulations provide an atomistic explanation of our experimental observations.

We synthesized poly(ethylene glycol) (PEG) networks by Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC) using three-arm star-PEG with azide end groups and linear PEG oligomers of different molar masses with alkyne end groups. After extensive characterization of the networks by 13C MAS and 1H multiple-quantum (MQ) NMR spectroscopy, their crystallization behavior is studied by differential scanning calorimetry (DSC), temperature dependent small and wide angle X-ray scattering (SAXS, WAXS) as well as 1H FID NMR. Since CuAAC introduces 1,4-disubstituted 1,2,3-triazole (TR) rings as chain defects into the network, we compare our results with those obtained from linear PEG which contained a purposely introduced TR ring in the middle of the polymer chain. PEG network chains are able to form the characteristic 72 helices upon cooling to −20 °C and crystallize into the monoclinic unit cell in complete analogy to the homopolymer. The crystallinity of the networks, though it is lower as compared to the linear samples, reached values of about 30–50%. Given the fact that the network chains are highly constrained in their configurational freedom, this is very surprising. However, cross-links and the TR defects have only a minor effect on the molecular dynamics of the PEG chains in the crystals since the characteristic αc-relaxation process (helix jumps) is also detected in the PEG networks by analysis of the 1H FIDs. The SAXS data reveal that randomly arranged stacks of lamellae are formed upon crystallization and the chains are tilted in the crystals at large angles of about 40°–55°. Supported by all experimental data, we propose a model to explain the formation of polymer crystals in the networks and concluded that primary and secondary loops which extent the network chains beyond the length of the linear precursors play an essential role for the crystallization.

We have used Cu(I)-catalyzed azide–alkyne cycloaddition to synthesize a new series of poly(ethylene oxide)s having in the center of their chains two 1,2,3-triazole (TR) rings separated by (CH2)n spacers with 2 ≤ n ≤ 4 (PEO11-TR-(CH2)n-TR-PEO11). The degree of crystallinity obtained by temperature-dependent WAXS measurements indicates that only one out of the two PEO11 chains of the three polymers forms a 72 helix upon cooling to −10 °C and crystallizes into a monoclinic unit cell known from PEO homopolymer. A solid-state phase transition occurs for all samples during heating below their melting temperature. Solid-state 13C MAS cross-polarization and single-pulse NMR spectroscopy indicate the complete incorporation of the chain defects into the PEO crystals (PEO-TR phase) during this transition. The 2D WAXS pattern of an oriented PEO11-TR-(CH2)2-TR-PEO11 sample generates a structural model where the crystal lattice of the initial PEO phase becomes highly distorted during the solid-state phase transition du...

A polyphosphoester (PPE) with phenyl phosphate groups separated by precisely 20 CH2 groups in its backbone was dissolved in chloroform and spread on the water surface of a Langmuir trough. The surface pressure vs area per monomer unit (π-A) Langmuir isotherm together with epifluorescence and Brewster angle microscopy suggested that some crystallization occurred already at zero surface pressure immediately after solvent evaporation of the spread polymer solution. The extended plateau region of the Langmuir isotherm in the range of π ≈ 4.5 mN m−1 corresponds to the 2D crystallization of most polymer chains. Brewster angle and epifluorescence microscopy show that during the crystallization of PPE in the Langmuir film single crystal like hexagonal entities are formed with lateral dimensions of up to 20 µm. These entities break upon compression beyond the limiting area per monomer unit which leads to a decrease of the elasticity modulus of the Langmuir film. The morphology of the single crystals and their failure upon compression are also observed in Langmuir-Blodgett films by atomic force microscopy. The thickness of the crystals is about 2.5 nm at the end of the plateau range and reaches 3.0 nm upon further compression. The polymer crystallization on the water surface is also confirmed by infrared reflection absorption spectroscopy.

Many text books and publications do not focus on the necessity of chain tilting in crystalline lamellae of oligomers and polymers, a fundamental aspect of their crystallization already discussed by Flory. Herein we investigate the chain tilt of ethylene oxide oligomers (EOs) containing various midchain defects by WAXS, SAXS and solid state 13C MAS NMR spectroscopy. At low temperatures, one out of the two EO chains of EO9-meta-EO9 and EO11-TR-EO11 containing a 1,3-disubstituted benzene or a 1,4-disubstituted 1,2,3-triazole defect in central position of the oligomer chain forms crystals and the other EO chain as well as the defect remain in the amorphous phase. The aromatic midchain defect of these two oligomers can be incorporated into the crystalline lamella upon heating below Tm. Then, the adjoining amorphous EO chain crosses from the lamellae to the amorphous regions at an angle ξ, which is preordained by the substitution pattern of the aromatic defect, revealing that the chain tilt angle ranges between...

Poly(glycerol adipate) (PGA) was synthesized by enzymatic polymerization and grafted with different amounts of oleoyl chloride. A series of graft copolymers PGA-g-Ox was obtained where O represents the oleate side chains and x is the degree of grafting (mol% of the pendant OH groups of PGA esterified) ranging from 11 to 90. Small angle X-ray scattering (SAXS) data revealed nanophase separation of the oleate side chains into nanodomains in bulk and wide angle X-ray scattering (WAXS) profiles showed a broad halo, reflecting the amorphous nature of the synthesized graft polymers. Glycerol monooleate (GMO), an amphiphilic lipid with one hydrophobic oleate tail and a glycerol hydrophilic head group, self-assembles into various liquid crystalline phases in the presence of water. Since oleate chains are integral part of both GMO and the graft copolymers, a certain degree of miscibility can be expected influencing the self-assembly behavior. Using SAXS for phase identification, systematic studies were carried out at room temperature on the ternary system of GMO/PGA-g-O22/water and the ternary phase diagram was constructed. The addition of polymer did influence the phase behavior of the GMO/water system. The water in the lamellar and cubic mesophases was partially replaced by PGA-g-O22. Furthermore, keeping the GMO/water ratio constant at 1:1, the addition of PGA-g-O22 lead to swelling of the water channels in the inverse bicontinuous Pn3m cubic phase. Preliminary investigations on the potential application of PGA-g-O22 as a stabilizer of structured nanoparticles in aqueous dispersions were carried out employing different transmission electron microscopy techniques.

Helical jumps in poly(ethylene oxide), which are the molecular processes underlying the intracrystalline chain diffusion, are studied on the microseconds to milliseconds time scale by means of NMR. Using a simple proton time-domain technique, a wide range of melt-crystallized morphologies is investigated ranging from extended-chain crystals of short chains to crystals with disordered fold surfaces of longer chains up to 190 kg/mol. From variable-temperature data we directly determine the Arrhenius activation parameters and find that the activation energy is always around 65 kJ/mol. At a given temperature, average correlation times vary from sample to sample over about 1 decade and increase approximately linearly with the lamellar thickness. The observed linear relation is reproduced by a generic Monte Carlo simulation model implementing a mechanism of diffusing defects. The experimental results are compared to 1D carbon-13 MAS exchange NMR (CODEX) and proton rotating-frame relaxation (R1ρ) data, for which...

The annular tautomerism of lithium 1,2,3-triazolate (Li-TR) is experimentally investigated in the solid state by X-ray diffraction and in methanolic solution by NMR spectroscopy. DFT-based ab initio molecular dynamics simulations are additionally carried out to characterize the solvation structure of Li-TR in methanol and to determine the free energy landscape of the two tautomers.

Poly(ethylene oxide) (PEO) is a polymer of great interest due to its prevalence in biomedical, pharmaceutical, and ion conductive systems. In this study, the crystallization behaviors of a PEO with 22 monomer units (PEO22) and a PEO having the same degree of polymerization but with an additional 1,4-disubstituted 1,2,3-triazole ring in central position of the chain (PEO11-TR-PEO11) are investigated. PEO11-TR-PEO11 shows one type of lamella crystal after cooling to T = 0 °C, but structural changes during heating below their final melting are detected by WAXS, DSC, POM, and solid-state NMR spectroscopy. The lamella thickness increases, but simultaneously the helix–helix distance decreases and an additional Bragg reflection appears at 2θ = 22.1°. A model is proposed which explains these structural changes by incorporation of the TR ring into the crystals which are additionally stabilized by attractive C–H···π interactions of the TR rings. Additionally, two different types of extended chain lamella crystals a...

Poly (e-caprolactone) (PCL) dissolved in chloroform was spread on the water surface of a Langmuir trough and after solvent evaporation, the surface pressure vs area (π-A) Langmuir isotherm was recorded. An extended plateau region indicates a 1st order phase transition related to PCL crystallization as also confirmed by Brewster angle microscopy (BAM). Infrared reflection absorption spectroscopy (IRRAS) and grazing incidence wide angle X-ray scattering (GI-WAXS) reveal details of the PCL crystallization process on a molecular level. The IRRAS and GI-WAXS experiments confirm that crystallization occurs at the plateau region of the π-A Langmuir isotherm. GI-WAXS also confirms that the polymer chains in the crystals are tilted by ≈ 21° with respect to the water surface normal direction. This value is consistent with IRRAS data at a maximum compression state of ≈ 2 A2.

Block copolymers consisting of blocks of poly(amino acid)s (PAAs) derived from naturally occurring l-amino acids and biocompatibilizing poly(ethylene glycol) (PEG) are of interest for biomedical applications because of their compatibility, partial degradability, and, depending on their molecular architecture, unique self-assembly behavior. PEGylated PAAs were synthesized by α-methoxy-ω-amino PEG-initiated ring-opening polymerization, ROP, of the N-carboxyanhydrides, NCAs, of l-leucine and l-glutamic acid γ-benzyl ester. The molecular weights of the resulting di- and triblock copolymers were well controlled with narrow polydispersities, and the block copolymers were obtained in high yields (>90 %). PEGylated PAA diblock copolymers with a copolymer block of PAAs were obtained when the amino acid NCAs were polymerized as a mixture and triblock copolymers with two PAA hompolymer blocks resulted from the successive addition of the respective NCAs. Dynamic light scattering indicated that these block copolymers self-assemble when exposed to a selective solvent into micelles with hydrodynamic radii between 7 and 10 nm, which aggregate into larger structures with radii ranging between 27 and 40 nm. The coexistence and sizes of the two types of particles were corroborated by small-angle neutron scattering analyses. A detailed analysis of the micelle core structures by transmission electron microscopy suggests that the cores of the micelles do not form perfect spheres and thereby enable their continued aggregation, which is further aided by the immiscibility and subsequent phase separation of poly(l-glutamic acid γ-benzyl ester) and poly(l-leucine) blocks that constitute the PAA block.

The chain mobility in crystals of a homopolymer of poly(ethylene oxide) (PEO) with 22 monomer units (PEO22) is compared with that of a PEO having the identical number of monomer units but additionally a 1,4-disubstituted 1,2,3-triazole (TR) point defect in the middle of the chain (PEO11–TR–PEO11). In crystals of PEO22, the characteristic αc-relaxation (helix jumps) is detected and the activation energy of this process is calculated from the pure crystalline 1H FIDs to 67 kJ/mol. PEO11–TR–PEO11 exhibits a more complex behavior, i.e. a transition into the high temperature phase HTPh is noticed during heating in the temperature range between −5 and 10 °C which is attributed to the incorporation of the TR ring into the crystalline lamellae. The crystal mobility of the low temperature phase LTPh of PEO11–TR–PEO11 is in good agreement with PEO22 since helical jump motions could also be detected by analysis of the 1H FIDs and the corresponding values of their second moments M2. In contrast, the high temperature ...

The behavior of crystallizable poly(e-caprolactone) (PCL) and poly(e-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) is studied at the air/water interface prior and after grafting to an amorphous poly(glycerol adipate) (PGA) backbone (PGA-g-PCL, PGA-g-(PCL-b-PEO)). Langmuir isotherms are measured and the structure formation in the monolayers on the water surface is followed by Brewster angle microscopy (BAM) and in Langmuir–Blodgett films after a transfer to silicon substrates by atomic force microscopy (AFM). It is observed that PGA-g-PCL forms significantly smaller crystals on the water surface and has smaller crystallization rate compared to PCL homopolymers of identical molar masses as the grafted chains. In contrast to crystals formed by linear PCL, the crystals formed by grafted PCL in PGA-g-PCL do not melt (readsorb at the water surface) in an expansion cycle on the Langmuir trough. Additionally, increasing the subphase temperature at constant surface area significantly above the melting point of linear PCL in bulk results in the formation of a mesophase, and it does lead to the disappearance of crystals. The isotherms of PGA-g-(PCL-b-PEO) show a transition at the surface pressure of ∼10 mN/m. This is related to the fact that PEO chains leave the water surface and submerge into the subphase and/or the crystallization of PCL chains. The monolayer collapse appears in an extended plateau region starting at π values of ∼30 mN/m. AFM images of Langmuir–Blodgett films reveal that PCL chains in PGA-g-PCL and PGA-g-(PCL-b-PEO) form lamellar crystals with a disk-shape and interconnected platelets, respectively.

A family of polyesters, poly(glycerol adipate) (PGA), poly(sorbitol adipate) and PGA-graft-poly(e-caprolactone), bearing OH groups on their backbones were synthesized by enzymatic polycondensation. They were successfully converted into macroinitiators for atom transfer radical polymerization (ATRP) by esterification with α-bromoisobutyryl bromide. As a proof of concept, glycerol monomethacrylate was polymerized by ATRP from a PGA backbone yielding the amphiphilic graft copolymer PGA-graft-poly(glycerol monomethacrylate). Its self-assembly in aqueous solution was studied using dynamic light scattering. © 2013 Society of Chemical Industry

Poly(ethylene glycol) (PEG) is often used to biocompatibilize surfaces of implantable biomedical devices. Here, block copolymers consisting of PEG and l-cysteine-containing poly(amino acid)s (PAA's) were synthesized as polymeric multianchor systems for the covalent attachment to gold surfaces or surfaces decorated with gold nanoparticles. Amino-terminated PEG was used as macroinitiator in the ring-opening polymerization, (ROP), of respective amino acid N-carboxyanhydrides (NCA's) of l-cysteine (l-Cys), l-glutamate (l-Glu), and l-lysine (l-Lys). The resulting block copolymers formed either diblock copolymers, PEG-b-p(l-Glux-co-l-Cysy) or triblock copolymers, PEG-b-p(l-Glu)x-b-p(l-Cys)y. The monomer feed ratio matches the actual copolymer composition, which, together with high yields and a low polydispersity, indicates that the NCA ROP follows a living mechanism. The l-Cys repeat units act as anchors to the gold surface or the gold nanoparticles and the l-Glu repeat units act as spacers for the reactive l-Cys units. Surface analysis by atomic force microscopy revealed that all block copolymers formed homogenous and pin-hole free surface coatings and the phase separation of mutually immiscible PEG and PAA blocks was observed. A different concept for the biocompatibilization of surfaces was followed when thiol-terminated p(l-Lys) homopolymer was first grafted to the surface and then covalently decorated with HOOC-CH2-PEG-b-p(Bz-l-Glu) polymeric micelles. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 248–257

Well-defined poly(ethylene glycol) (PEG) networks were synthesized using copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC). Two types of PEG network structures were prepared (i) by linking two three-arm star PEG oligomers together and (ii) by connecting three-arm PEG star units with bifunctional linear PEG oligomers of different molar masses. End-group functionalization of PEG oligomers to azide and alkyne moieties was performed while for CuAAC the catalytic system of CuSO4 and sodium ascorbate in aqueous environment was used. The successful conversion of the precursors and the formation of networks were confirmed by 13C-MAS NMR and FTIR spectroscopy. Network defects like multiple links and dangling chain ends were quantitatively investigated by 1H double quantum (DQ) NMR spectroscopy.

We studied the behavior of monolayers at the air/water interface of T-shaped facial amphiphiles which show liquid-crystalline mesophases in the bulk. The compounds are composed of a rigid p-terphenyl core (TP) with two terminal hydrophobic ether linked alkyl chains of equal length and one facial hydrophilic tri(ethylene oxide) chain with a carboxylic acid end group. Due to their amphiphilic nature they form stable Langmuir films at the air/water interface. Depending on the alkyl chain length they show markedly different compression isotherms. We used infrared reflection absorption spectroscopy (IRRAS) to study the changes in molecular organization of the TP films upon compression. We could retrieve information on layer thickness, alkyl chain crystallization, and the orientation of the TP cores within the films. Films of TPs with long (16 carbon atoms: TP 16/3) and short (10 carbon atoms: TP 10/3) alkyl chains were compared. Compression of TP 16/3 leads to crystallization of the terminal alkyl chains, whereas the alkyl chains of TP 10/3 stay fluid over the complete compression range. TP 10/3 shows an extended plateau in the compression isotherm which is due to a layering transition. The mechanism of this layering transition is discussed. Special attention was paid to the question of whether a so-called roll-over collapse occurs during compression. From the beginning to the end of the plateau, the layer thickness is increased from 15 to 38 Å and the orientation of the TP cores changes from parallel to the water surface to isotropic. We conclude that the plateau in the compression isotherm reflects the transition of a TP monolayer to a TP multilayer. The monolayer consists of a sublayer of well-organized TP cores underneath a sublayer of fluid alkyl chains whereas the multilayer consists of a well oriented bottom layer and a disordered top layer. Our findings do not support the model of a roll-over collapse. This study demonstrates how the IRRA band intensity of OH or OD stretching vibrations can be used to retrieve information about layer thickness and refractive indices of the film and how multicomponent IRRA bands can be fitted to retrieve information about the orientation of molecules within the monolayer.

Well-defined perfluoroalkyl-terminated poly(glycerol methacrylate) (R F-PGMA) semitelechelics are prepared by atom transfer radical polymerization and copper(I)-catalyzed alkyne–azide cycloaddition reaction. R F-PGMA has a similar architecture as the well-studied perfluorinated poly(ethylene oxide) (R F-PEO) semitelechelics but bears two hydroxyl groups on each glycerol methacrylate unit. Because of the strong hydrophobic interaction of the perfluoroalkyl group, R F-PGMA semitelechelics self-associate to form core–corona spherical micelles in water above the critical micellization concentration (cmc) which depends on poly(glycerol methacrylate) (PGMA) content and temperature. For comparison, the R F-PEO semitelechelics with the same perfluoroalkyl terminal group as R F-PGMA are also prepared. The cmc values of R F-PGMA semitelechelics are found to increase with increasing temperature in water, which is opposite to the tendency of R F-PEO semitelechelics. According to the thermodynamic studies, the micellization process of R F-PGMA in aqueous solution is driven by both a negative enthalpy and an increase of entropy, whereas the micellization of R F-PEO is an entropy-driven process exhibiting a positive micellization enthalpy. This striking different behavior originates from intra-/intermolecular hydrogen bonds between the hydroxyl groups of the PGMA chains. These strong inter- and intramolecular hydrogen bonds between PGMA segments lead to a self-aggregation of R F-PGMA evident in temperature-dependent 1H and 19F NMR spectroscopy and dynamic light scattering measurements.

Chiral poly(glycerol methacrylate)s (PGMAs) are synthesized via ATRP using enantiopure solketal methacrylates followed by acidic hydrolysis. The optical activity of the polymers is confirmed by measurements of the circular dichroism. Furthermore, the chirality of the PGMAs containing repeat units with diol groups is determined via 1 H NMR spectroscopy employing a three-component chiral derivatizing process, involving the treatment of enantiopure polymers with 2-formylphenylboronic acid and enantiopure α-methylbenzylamine (MBA), which yields cyclic boronate diastereoisomers on the pendant groups. The detection of the chirality of the PGMAs is based on the anisotropic shielding/deshielding effect of the phenyl group in ( R )- or ( S )-MBA. The main advantage of this method is its simplicity as it only involves the mixing of all the components without any further purification steps. This procedure has been applied here for the first time to chiral polymers.

Interactions of the phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) with the amphiphilic diblock copolymer Ch-lPEG30-b-hbPG24 (ChP) are studied at the air–water interface by surface pressure–mean molecular area (π–mmA) measurements of mixed Langmuir films and adsorption measurements of ChP to the air–water interface covered with DPPC monolayers at different initial surface pressure values π0. ChP is composed of a single hydrophobic cholesteryl (Ch) moiety covalently bound to a diblock copolymer consisting of a hydrophilic linear poly(ethylene glycol) (lPEG) block and a hydrophilic hyperbranched poly(glycerol) (hbPG) block. Langmuir isotherms and compression moduli of the mixed Langmuir films of different molar ratios reveal distinct interactions between DPPC and ChP during compression. It is demonstrated that the behavior of the DPPC/ChP mixtures is dominated by DPPC up to a molar ratio of 10:1, whereas the behavior is predominantly governed by ChP in mixtures with lower DPPC content (molar ratios of 5:1, 2:1, and 1:1). In adsorption measurements, a strong affinity of ChP to DPPC is observed after injection into the water subphase. The surface pressure value πin up to which ChP is able to penetrate into DPPC monolayers is determined to the remarkably high value of 48.2 mN/m which attests the favorable interactions between DPPC and the Ch moiety of ChP. Atomic force microscopy on LB films of DPPC/ChP mixtures of different molar ratios transferred onto hydrophilic substrates confirms the presence of two different phases, a DPPC-rich phase and a ChP-rich phase.

The pressure–volume–temperature (PVT) behaviour of styrene–acrylonitrile (SAN) random copolymers and of tetramethylbisphenol A oligosulfones (TMOS) was studied using the Flory–Orwoll–Vrij (FOV) as well as the Sako–Wu–Prausnitz (SWP) equation-of-state (EOS). It was found that the SWP EOS is superior to the FOV theory in describing the PVT behaviour of the polymers, especially in the high-pressure range. Furthermore, blends comprising TMOS and SAN copolymers of varying acrylonitrile content were studied by means of cloud point measurements and differential scanning calorimetry. The system shows pronounced miscibility-window behaviour, i.e. the miscibility depends strongly on the copolymer composition. At the edges of the miscibility window, UCST (upper critical solution temperature) behaviour was observed and discussed in terms of the FOV EOS. The cloud point curves were exceptionally broad and could be reproduced neither by the Flory–Huggins nor by the FOV theory. However, taking the polydispersity of both components into account, the calculation of correct phase diagrams was possible using the FOV theory. Exchange energy parameters between the polymers, XAB, were obtained from fitting the critical points of the phase diagrams. Additionally, segmental exchange energy parameters Xi/j of the components were calculated.

A simple approach using comb-like polymers that undergo nanophase separation between the polyester backbone and the stearoyl side chains is proposed for the preparation of structured non-spherical nanoparticles from a nanoemulsion. Depending on the degree of esterification of the OH groups of poly(glycerol adipate) differently ordered nanostructures is obtained. A perfect lamellar arrangement is obtained for polymers with a high degree of esterification and leads to spherical nanoparticles with an internal onion-like structure. However, when the degree of esterification is only 20 mol%, polygonal nanoparticles with an internal pseudo-hexagonal structure are obtained. The differences in the nanoparticle shapes are related to the volume fraction of the paraffinic pool.

Blends of poly(ethylene oxide) (PEO) and poly(methyl acrylate) (PMA) as well as the respective diblock copolymers PEO-b-PMA form a homogeneous melt and undergo crystallization of PEO upon cooling. Although an identical PEO (Mn = 5000 g/mol) is used in blends and diblock copolymers, crystallization and melting behavior at comparable PMA contents differs strongly as revealed by temperature-resolved small-angle X-ray scattering (TR-SAXS) and differential scanning calorimetry (DSC) measurements. After isothermal crystallization, PEO lamellae in the blends thicken during heating from once-folded to extended chain crystals prior to melting as revealed by TR-SAXS. Contrarily, in PEO-b-PMA a thickening to extended chain lamellae is impossible when the PMA block exceeds an Mn of about 3000 g/mol. This behavior is caused by a balance between the tendency of the crystallizable block to form extended chain crystals, the tendency of the noncrystallizable chains to adopt a maximum in conformational entropy, and the spa...

A series of amphiphilic diblock copolymers and triphilic triblock copolymer analogues of the architectures BA, CAB, and CBA have been synthesized and characterized with respect to their aggregation behavior in water. The A, B, and C components of the block copolymers are formed by hydrophilic poly(glycerol monomethacrylate) (PGMA), lipophilic poly(propylene oxide) (PPO), and a fluorophilic perfluoroalkyl segment, respectively. Their critical micelle concentrations in water are determined from surface tension measurements. The aggregation behavior of the copolymers, as investigated by DLS, SANS, AFM, and TEM, is found to be governed by the strong immiscibility between the lipophilic PPO blocks and the fluorophilic perfluorocarbon segments as well as the blocks sequence. It is found that the BA and CBA copolymers form clear micellar solutions in contrast to the CAB copolymer solutions which exhibit phase-separation above the LCST of the PPO block.

The pressure–volume–temperature behavior of miscible blends of poly(ethylene oxide) (PEO) and poly(methyl acrylate) (PMA) was studied over extended ranges of temperature and pressure. From pressure–volume–temperature data, the reduction parameters for the Flory-Orwoll-Vrij equation-of-state were determined. It was found that reduction parameters as well as density, thermal expansion coefficient, and isothermal compressibility vary with composition in a nonlinear manner. The surface tension of the blends in the molten state was measured over the whole composition range using the sessile drop method. The surface tension was found to display negative deviation from additivity pointing toward a remarkable surface excess of PMA. Moreover, surface tension displays a minimum in the range of low PEO content at weight fraction of ∼0.19. In addition, the temperature coefficient of surface tension shows negative deviation from linearity. It stays constant when PMA is in excess. Results are discussed in terms of equation-of-state thermodynamics. The minimum of surface tension can be well explained by weak self-association of PEO in the bulk. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1893–1900, 2010

This study describes the responsive behavior of modified amphiphilic ABA triblock copolymers of polymethyloxazoline-block-poly(methylhydrosiloxane-co-dimethylsiloxane)-block-polymethyloxazoline (PMOX-b-P(MHS-co-DMS)-b-PMOX) when subjected to compression on the water surface or to ions in the water bulk phase. The hydrophobic middle block was functionalized with spacers bearing methyl 2-hydroxybenzoate (Bz) or 18-crown-6 ether (Ce) groups. The behavior at the air–water interface was studied by measuring surface pressure versus mean molecular area (π–mmA) isotherms, and atomic force microscopy (AFM) was employed to investigate the morphology of Langmuir–Blodgett (LB) films after transfer to solid supports. Ion-responsive self-assembly was followed using light microscopy and can be understood on a molecular level by employing 1H NMR spectroscopy. The π-mmA isotherm of PMOX-b-P(MHS-co-DMS)-b-PMOX-44Bz at the air–water interface had an extended pseudo-plateau at a surface pressure of ca 22 mN m−1 reflecting the coil to loop transformation of the hydrophobic middle block which was absent for the crown ether-functionalized triblock copolymer. AFM images of LB films of PMOX-b-P(MHS-co-DMS)-b-PMOX-44Bz showed dewetting effects of the polymer film after transfer to a silicon wafer. LB films of PMOX-b-P(MHS-co-DMS)-b-PMOX-8Ce formed surface micelles having a size of ca 50–100 nm on the solid support. The ion sensitivities of the crown ether-derivatized copolymers in solution were investigated by exposing polymeric vesicles to potassium, sodium and magnesium ions. Exposure to K+ and Na+ led to vesicle rupture and the formation of micro-tubular structures, while Mg2+ had no effect on the vesicular structures as confirmed using light microscopy. Specific interactions between the crown ether-derivatized polymer and ions were further elucidated from 1H NMR experiments that indicated that K+ coordinated with the crown ether causing the dense packing to subside and leading to solubilization of the polymer in water. Copyright © 2010 Society of Chemical Industry

The tremendous influence of hydrophilic block length tuning on the aggregation behavior of novel water-soluble triphilic (i.e., hydrophilic, lipophilic, and fluorophilic) α,ω-perfluoroalkyl end-capped symmetric ABA triblock copolymers is demonstrated. The hydrophilic A and lipophilic B blocks are comprised of poly(glycerol monomethacrylate) (PGMA) and poly(propylene oxide) (PPO), respectively. The fluorophilic component consists of two “clicked” perfluoroalkyl segments (C9F19) at the ends of the block copolymers. Two of the different block copolymers synthesized, namely F9-PGMA24-PPO27-PGMA24-F9 (PB1) and F9-PGMA42-PPO27-PGMA42-F9 (PB2), differ only in the degree of polymerization of the hydrophilic PGMA blocks. Their critical micelle concentrations in water are determined from surface tension measurements. The aggregation behavior in aqueous medium studied by 19F NMR spectroscopy reveals that the fluorocarbon component forms part of the micelle corona of PB1, while in PB2 it aggregates to form part of th...

The synthesis of three-arm-star (PIB-PEO) block copolymers (BCPs) via azide/alkyne "click" reaction and their behavior at the air/water interface are reported. Starting from a three-arm-star allyl-telechelic PIB (1) prepared by living cationic polymerization, the three-arm-star PIB-(CH 2 N 3 ) 3 (2c) was generated via borane addition/oxidation PIB-(CH 2 OH) 3 , (2a) followed by reaction with CBr 4/ PPh 3 furnishing PIB-(CH 2 Br) 3 (2b) and then the PIB-(CH 2 N 3 ) 3 (2c) after reaction with trimethylsilyl-azide/tetrabutylammonium fluoride. The final three-arm-star (PIB-PEO) BCPs (4a, 4b) were then generated by azide/alkyne "click" reaction of the PIB-(CH 2 N 3 ) 3 (2c) with alkyne-telechelic PEOs (3a, 3b) in a biphasic water/toluene mixture, using copper(II) sulfate pentahydrate/sodium ascorbate as the Cu(I)-regenerative system and microwave irradiation. NMR spectroscopy and MALDI investigations proved the final structure of the three-arm-star PIB-PEO BCPs. Subsequent Langmuir- and Langmuir-Blodgett films investigations of 4a and 4b reveal the absence of a pancake-to-brush transition. Compared to PIB 54 - (PEO 3 -OCH 3 ) 3 4a, the collapse of PIB 54 -(PEO 16 -OCH 3 ) 3 4b occurs at higher surface pressures and lower mean molecular area values indicative of stronger anchoring of the PIB block to the air/water interface. Addition of iron-oxide nanoparticle (R h = 83 A) leads to a stabilization of the hydrophobic layer of 4a, thus shifting the collapse to higher surface pressures.

Two hydrophobically modified PNIPAM semitelechelics P x F 9 were prepared by "clicking" PNIPAM containing an azide endgroup (P x N 3 ) with nonadecafluoro-1-decyl hex-5-ynoate (F 9 ). Micelles of P x F 9 in water with a core of F 9 -segments and a PNIPAM corona were detected by dynamic light scattering and by 1 H and 19 F NMR spectroscopy below the LCST. Just below the LCST, the PNIPAM chains start to collapse onto the F 9 core followed by aggregation of several collapsed micelles to large particles in the range of ≈110 nm. The F 9 segments shifted the LCST to lower temperatures when comparing P x N 3 with P x F 9 . The existence of micelles in P x F 9 solutions also improved the reversibility of the LCST behavior as measured by DSC.

The bulk of literature on phospholipid membrane interactions with non-ionic amphiphilic block copolymers deals with ABA triblock copolymers of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide). This is partially the result of their commercial availability. In recent years novel block copolymers have been synthesized and their interactions with phospholipids structured as Langmuir monolayers, liposomes, bilayer lipid membranes, tethered bilayers, and living cells have been studied. This review describes some new block copolymers with potential to interact with phospholipids. There is a tremendous progress in synthesis of amphiphilic block copolymers triggered by new controlled polymerization techniques as atom transfer radical polymerization or nitroxide mediated polymerization and by the possibility to ‘click’ preformed blocks together using quantitative reactions of functional endgroups. A special focus is given to novel water soluble amphiphilic triblock copolymers of poly(glycerol monomethacrylate)-b-poly(propylene oxide)-b-poly(glycerol monomethacrylate) and their interactions with phosphatidylcholine lipids. Also block copolymers containing hydrophobic blocks with perfluoroalkyl groups are discussed since they are special in a sense that their fluorophilic blocks are neither hydrophilic nor oleophilic as this is the case for conventional amphiphilic block copolymers. Experimental methods to study block copolymer–phospholipid interactions are summarized and selected results based on special experimental techniques such as isothermal titration calorimetry, infrared reflection absorption spectroscopy and ion conductance are presented. This work is intended to convey a better quantitative understanding of amphiphilic block copolymers used for in vitro and in vivo experiments in medicine and pharmacy.

Pressure-volume-temperature and surface tension behaviour were studied for random copolymers of styrene and acrylonitrile (SAN) and for poly(butylene terephthalate) (PBT). Results served to determine reduction parameters for the equation-of-states by Flory-Orwoll-Vrij and by Simha-Somcynsky as well. Surface tension as a function of copolymer composition displays negative deviation from additivity. It indicates surface excess of styrene units. Similar behaviour with respect to copolymer composition was found for variation of interfacial tension between SAN and PBT. Thickness of surface region is around 1 nm and does not change with copolymer composition whereas extension of interfacial region between PBT and SAN copolymers varies strongly with copolymer composition between around 2 and 60 nm.

Poly[(2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate)] [poly(solketal methacrylate) (PSMA)] was synthesized by free radical polymerization. By partial hydrolysis of the acetal group, random copolymers of SMA with 2,3-dihydroxypropyl methacrylate (DHPMA) were synthesized whereas complete cleavage lead to poly(2,3-dihydroxypropyl methacrylate) (PDHPMA). The copolymer composition was determined by 1H NMR spectroscopy. FTIR spectroscopy indicates the synthesis of random copolymers with different degrees of hydrogen bonding as measured by a shift of the OH vibration bands. The glass transition temperature of the random copolymers increases linearly with increasing DHPMA content, resulting in a positive deviation from the Fox equation. The thermal degradation of both homopolymers and their random copolymers has been studied. Finally, the solution behaviour of the copolymers and PDHPMA in water studied by dynamic light scattering showed a strong tendency of the polymer chains to form clusters in the size range of 15–62 nm. The size and the kind of associating interactions within the clusters strongly depend on the copolymer composition.

Pressure–volume–temperature (PVT) data were studied for ethylene–vinyl alcohol random copolymers (EVOH) and served to determine bulk reduction parameters for the equation-of-state by Flory–Orwoll–Vrij. The compressibility factor as a function of copolymer composition displays positive deviation from additivity. Sessile drop method yielded surface tensions of EVOH melts at different temperatures. To a good approximation linear variation of surface tension with respect to copolymer composition was observed. It indicates that conformational restrictions prevent surface excess of the low-energy units. Results on surface tensions are discussed in terms of different theoretical approaches. It turns out that the parachor approach is in excellent agreement with experimental data. The corresponding state approximation revealed decreasing surface energy with ascending ethylene content whereas the surface entropy remains approximately constant as long as vinyl alcohol units are in excess.

The adhesion and interfacial properties of polyurethane (PU) foams with thermoplastic (TP) materials were investigated using different techniques. The adhesion performance of PU foam with TP materials was evaluated using the peel test method, and the adhesion durability was checked after different climate treatments. X-ray pho- toelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements were used to study the surface and interface morphology of PU foam and TP material system. Three types of PU foam samples which differ in their composition and also five commer- cially available TP blends systems, based on poly(carbon- ate), poly(styrene-co-maleic anhydride), poly(acrylonitrile- butadiene-styrene), and silicone acrylate rubber have been used. The slow reacting foam shows the best adhesion properties with all the TP materials. The climate treat- ments strongly effected the PU foam adhesion durability with poly(carbonate) containing TP materials (70-80% loss in adhesion), but nearly no effect with poly(styrene-co-ma- leic anhydride). The samples with lowered adhesion could be separated by peeling without visible foam residues on the TP surface. AFM, XPS, and surface tension studies have shown that the surface properties of the TP material are still governed by the PU foam. 2007 Wiley Periodicals

A series of novel water-soluble amphiphilic triblock copolymers having ABA architecture has been synthesized via atom transfer radical polymerization (ATRP) technique. The blocks comprised a thermoresponsive poly(propylene oxide) (PPO) middle block with a molar mass of around 2000 g·mol-1 and two hydroxy-functional poly(2,3-dihydroxypropyl methacrylate) (also named poly(glycerol monomethacrylate) (PGMA)) outer blocks with lengths varying from 14 to 221 monomeric units per block, which account for the solubility in water. Gel permeation chromatography analysis confirmed unimodal molar mass distributions with polydispersity indexes ranging between 1.29 and 1.40. Their association behavior in aqueous solutions was studied. The size of the micelles formed and the thermal dependence of the micellization process were followed by dynamic light scattering at different temperatures. Depending on the length of the PGMA blocks, micelles showed an average hydrodynamic diameter in the range from 20 to 30 nm. Critical ...

Langmuir monolayers and Langmuir–Blodgett (LB) film morphology of amphiphilic triblock copolymers are studied using surface pressure-area measurements and atomic force microscopy (AFM), respectively. The triblock copolymers are composed of long water-soluble poly(ethylene oxide) (PEO) chains as middle block with very short poly(perfluorohexylethyl methacrylate) (PFMA) end blocks. The surface pressure-area isotherms show phase transitions in the brush regime. This phase transition is due to a rearrangement of PFMA block at the air–water interface. It becomes more significant with increasing PFMA content in the copolymer. LB films transferred at low surface pressures from the air–water interface to hydrophilic silicon substrates show surface micelles in the size range of 50–100 nm. A typical crystalline morphology of the corresponding PEO homopolymer is observed in LB films of copolymers with very short PFMA blocks, transferred in the brush region at high surface pressure. This crystallization is hindered with increasing PFMA content in the copolymer.

Two series of novel α,ω-perfluoroalkyl terminated esters of poly(ethylene oxide) (PEO) (R F -PEO) having the general structure C m F 2m+1 -COO-(CH 2 -CH 2 -O) n -OC-C m F 2m+1 , with m = 1,2,3,4 or 5 have been synthesized. The influences of the PEO molar mass, the length of the perfluoroalkyl group (R F ) and temperature on the cleavage of the ester bridge in aqueous solution and the effect of the hydrolysis process on the size of aggregates formed in water were studied. According to 1 H and 19 F NMR measurements the degree of functionalization obtained (up to 96 mol-%) increases with the decrease in the length of the R F group. All of the derivatives showed ester cleavage in water in short time scales. The rates of hydrolysis of the ester bridge in aqueous solution were determined from pH-measurements. It was verified that the rate law for hydrolysis corresponds to a pseudo-first order type. The hydrolysis kinetic constant k increased with a decrease in the length of the R F group ranging from 0.2 x 10 -3 s -1 for the longest R F group (C 5 F 11 -) up to 1.2 × 10 -2 s -1 for the shortest R F group (CF 3 -). The value of k depended almost exclusively on the length of the perfluoroalkyl chain and was independent of the length of the PEO backbone (1 000 or 2 000 g mol -1 ), as long as no additional phenomenon such as phase separation was present. It was also found that the change in the value of k with temperature followed a non-Arrhenius pattern and there was an evident relationship between the non-linearity in the In k vs. 1/Trelation with increasing temperatures and the occurrence of a macroscopic phase separation of LCST type. Dynamic light scattering measurements showed the coexistence of unimers with associated species with apparent hydrodynamic radii (R h ) of approximately 20-45 nm for all samples in aqueous solutions. These species might correspond to aggregates of a few micelles. For some samples also larger aggregates were found with R h in the 100-500 nm range, which might be attributed to clusters of micelles.

The aim of this study was to investigate the structure and morphology of polyurethane (PU) foams at the interface with a thermoplastic material. Fourier trans- form infrared/attenuated total reflectance spectroscopy was used to study the reaction of 4,4-diphenylmethane diisocya- nate (MDI) with polyether-based polyols with water as a blowing agent via the absorption intensity of the (NCO, 2265 cm 1 ) vibrational band of MDI in three different PU foam systems. The data revealed that MDI reacted simulta- neously with two different species in the reaction mixture having different reaction rates. These were the reactions of isocyanate functional groups with water (fast reaction) and polyol (slow reaction). A structure analysis at the PU foam interface (i.e., PU formed a compact film 110 30 m thick at the interface) with a thermoplastic material plate was carried out with small-angle X-ray scattering (SAXS), trans- mission electron microscopy (TEM), and neutron reflection (NR) techniques. From SAXS measurements, a typical hard- segment-segment distance of 10 0.3 nm was observed. The TEM and NR data of the compact PU film revealed an internal layered structure (parallel to the surface) with a typical layer thickness of 260 - 400 nm. The formation of a layered morphology (macrophase-separated structures) was assumed to be due to the difference in the polarities of the hard and soft segments. Furthermore, the layer thickness increased when D2O was used as the blowing agent instead of H2O. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1280 -1289, 2005

Bulk polymerisations of e-caprolactone (CL) were conducted at 170 � C in the presence of catalytic traces of water and 10, 30 and 50 wt% of hydrated synthetic montmorillonite SOMASIF ME100 (M) without additional catalysts. In both cases a low molecular poly(e-caprolactone) (PCL) was produced (Mw = 5360–22,432). As revealed by 1 H NMR and GPC analyses the montmorillonite present in the system induced both significantly higher lactone hydrolysis and polymer chain growth rates. Wide-angle X-ray scattering (WAXS) technique was applied to investigate the changes in clay stratification after swelling with monomer and after the polymerisation. The scattering peaks from clay (0 0 1) periodicity recorded for the silicate in dispersions and in the composites are shifted towards lower angles, which indicate an intercalation of CL as well as PCL in the galleries. Narrow intensity distribution of Bragg peaks recorded for both CL/M mixtures and resulting nano-intercalates testifies that the well ordered, layered structure of montmorillonite is retained in the silicate swollen with e-caprolactone and after the polymerisation. The results suggest that PCL chains are flatly arranged onto each side of silicate platelet and they create pseudo-bilayers inside the silicates gallery. � 2004 Elsevier Ltd. All rights reserved.